Flexible couplings are used to transmit a rotational force from a rotatably driven shaft to a coaxially aligned shaft. One particular coupling includes a resilient coupling member molded in an annular shape to fit around two substantially identical hubs. Each hub is mounted to one of the shaft ends, and has circumferentially spaced receptacles. The coupling member has projections which are received in the receptacles, and are interposed between the hubs to transfer the rotational force from one hub to the other. An endless metal retainer ring is slipped over the belt to secure the teeth in the receptacles. The coupling member is produced in a plurality of sizes (i.e. different diameters) to fit different sized hubs.
These couplings, advantageously accommodate minor shaft misalignments between the shafts which can result from manufacturing or assembly errors. Because of the advantages inherent in the flexible coupling they are used throughout the world, and are available in a wide range of sizes. When a coupling does fail, it is often a result of the resilient coupling member failing, and therefore, as a part of routine maintenance, these coupling members are replaced on a regular basis. If a facility has a number of the couplings of varying sizes, a coupling member for each coupling size must be stocked.
In addition, the coupling retainer ring has a tendency to “walk off” the coupling member if the shafts are grossly misaligned. As disclosed in U.S. Pat. No. 5,738,585, one method for retaining the ring on the coupling member is to form a radially inwardly extending rigid pin on an inner surface of the ring which engages an axial slot formed on the radially outwardly facing surface of the coupling member. Various methods are known to hold the pin over the coupling member, such that the ring does not walk off the coupling. Manufacturing the ring with the inwardly extending rigid pin is expensive, and the coupling member must have an outwardly facing surface which is sufficiently rigid to hold the pin in place. Moreover, if the rigid pin breaks off of the ring, an alternative means of retaining the ring over the coupling member is required, or a new ring must be provided.